In the oil and gas industry, the purpose of a reamer is to size the well bore to a specific diameter. Reamers have been around probably as long as oil wells have been drilled. Standard reamers have fixed blades or rollers (roller reamers), with blades of certain lengths and number of sets of blades or rollers. Key seat wiper reamers are used to back ream a key seat that is created when a well deviates and the pipe wears into a softer formation.
Reamers used in horizontal wells size the well's diameter over a certain course length. Solid fixed reamers can be any number of blades, in any number of sets of blades a certain distance apart. Trouble with fixed reamers is when they are lowered into a deviated well bore with too much force, they tend to have elevated over pull to remove it from the dogleg. If the force applied is too great and the reamer does not go through the dogleg it may become stuck. When pulling up, the two and three fixed blade reamers have more over pull because all the blades have to be freed from their stuck positions at the same time.
Applicant has developed an improved reamer that provides multiple sets of cutting elements along its length, but arranges them in a unique configuration of fixed and movable sets to allow for easier removal in the above scenario.